They could be filling in the passwords with a random string and then using the browser extension to replace it when the form is submitted. You might be able to

They could be filling in the passwords with a random string and then using the browser extension to replace it when the form is submitted. You might be able to view the password using something like https://addons.mozilla.org/en-us/firefox/addon/tamper-data/ https://addons.mozilla.org/en-us/firefox/addon/tamper-data/ provided that runs after their extension.